→ ERK1*|T_pho|Y_pho|active@Cytosol References
PMID:8388392
PMID:8226933
In the cytoplasm activated MEK1 (Serine phosphorylated) may encounter monomeric, inactive ERK1.
ERK1 in its inactive form is not phosphorylated on a critical Threonine (T) and a critical Tyrosine (Y).
MEK1 phosphorylates the critical Tyr and Thr on ERK1, converting two ATP to ADP. Phosphorylation of ERK-1 activates its kinase activity.